1
MCQ (Single Correct Answer)

### AIPMT 2010 Prelims

Which one of the following compounds is a peroxide?
A
KO2
B
BaO2
C
MnO2
D
NO2

## Explanation

2
MCQ (Single Correct Answer)

### AIPMT 2010 Mains

The compound A on heating gives a colourless gas and a residue that is dissolved in water to obtain B. Excess of CO2 is bubbled through aqueous solution of B, C is formed which is recovered in the solid form. Solid C on gentle heating gives back A. The compound is
A
CaCO3
B
Na2CO3
C
K2CO3
D
CaSO4$\cdot$2H2O

## Explanation

A $\buildrel \Delta \over \longrightarrow$ colourless gas + residue

Residue + H2O $\to$ B $\buildrel {excess\,\,C{O_2}} \over \longrightarrow$ C $\buildrel \Delta \over \longrightarrow$ A

This is possible only when ‘A’ is CaCO3. The reactions are as follow :

3
MCQ (Single Correct Answer)

### AIPMT 2010 Prelims

Which of the following alkaline earth metal sulphates has hydration enthalpy higher than the lattice enthalpy?
A
CaSO4
B
BeSO4
C
BaSO4
D
SrSO4

## Explanation

The hydration enthalpy of BeSO4 is higher than its lattice energy. Within group 2, the hydration energy decreases down the group while lattice energy is almost the same.
4
MCQ (Single Correct Answer)

### AIPMT 2010 Prelims

Property of the alkaline earth metals that increases with their atomic number
A
solubility of their hydroxides in water
B
solubility of their sulphates in water
C
ionization energy
D
electronegativity

## Explanation

On moving down the group, basic nature of these hydroxides increases due to low ionization enthalpies because M-O bond in MOH is weak and thus break to give OH ions in the solution.

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